Bicomponent polyester textile filament

ABSTRACT

A crimpable composite textile filament having two longitudinally extending components, one of said components consisting essentially of poly(1,4-cyclohexylene dimethylene terephthalate) and the other component consisting essentially of poly(ethylene terephthalate).

Unified Stees stem Edward A. Haseley Grifton;

Elmer E. Most, Jr., Kinston, both of N.C. 853,192

Aug. 26, 1969 Dec. 7, 1971 E1. du Pont de Nemours and Company Wilmington, Del.

lnvemors Appl. No. Filed Patented Assignee BICOMPONENT POLYESTER TEXTILE BY,157 MS,157;28/72.17;264/171, 168;

[56] References Cited UNITED STATES PATENTS 3,181,224 5/1965 Tanner 57/140 X 3,315,021 4/1967 Luzzatto 264/168 3,350,871 11/1967 Pierce et a1. 57/140 3,454,460 7/1969 Bosley 161/173 3,458,390 7/1969 Ando et a1. 161/177 3,520,770 7/1970 Shima et a1. 161/173 Primary Examiner-1ohn Petrakes Attorney-John E. Dull ABSTRACT: A crimpable composite textile filament having two longitudinally extending components, one of said components consisting essentially of poly( 1,4-cyc1ohexylene dimethylene terephthalate) and the other component consisting essentially of poly(ethylene terephthalate).

BICOMPONENT POLYESTER TEXTILE FILAMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to composite textile filaments and more particularly to improved self-crimping polyester composite filaments.

2. Prior Art Composite filaments are well-known. Such filaments usually consist of at least two different longitudinally extending components which shrink differently when the filaments are appropriately treated, e.g. with hot water. The components are usually arranged in an eccentric manner relative to the fiber axis so that the shrinkage treatment causes the filament to develop a spiral crimp with the higher shrinking component predominantly on the inside of the helix. Such filaments may be produced by extruding two different synthetic polymers in side-by-side or eccentric sheath-core relationship. A major advantage of composite filaments compared to mechanically crimped filaments is the fact that with composite filaments the crimp may be developed partially or completely after the filaments have been processed into fabric.

Suitable composite filaments from melt-spinnable polymers have been prepared from combinations such as polyamides and polyesters or polyamides and copolyamides. Since polyester fibers have desirable qualities which are not found in most fibers from melt-spinnable synthetic polymers, practitioners of the art have tried to find combinations of polyesters which can be used to produce composite filaments with adequate crimpability. However, it has been difficult to find polyester/polyester combinations which exhibit satisfactory properties, primarily because most polyesters must be annealed to crystallize and thus stabilize the polyesters against excessive shrinkage in the fabric. The annealing treatment however usually reduces the difference in shrinkage between the components to a level where satisfactory crimpability under restraint is not attained.

SUMMARY OF THE INVENTION The present invention provides a crimpable composite textile filament having two longitudinally extending components, one of said components consisting essentially of poly( 1,4- cyclohexylene dimethylene terephthalate) and the other component consisting essentially of poly(ethylene terephthalate), said poly( 1,4-cyclohexylene dimethylene terephthalate) component being 15 to 70 percent, or preferably 30 to 60 percent by weight of said filament. The filaments of this invention are characterized by an ability to attain a satisfactory crimp level under restraining forces such as imposed in fabrics. Fabrics made from these filaments have excellent wash-wear performance. Crimped staple fibers from the filaments of this invention provide wool blend, cellulose blend, and 100 percent polyester fabrics with good cover and resilience.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The filaments of this invention are prepared by extruding the poly(1,4-cyclohexylene dimethylene terephthalate) and poly(ethylene terephthalate) in side-by-side or eccentric sheath-core relationship to form composite filaments, quenching the extruded filaments, drawing the filaments and heating them to stabilize the fiber structure. The poly(1,4- cyclohexylene dimethylene terephthalate) component constitutes 15 to 70 percent, or preferably 30 to 60 percent, by weight of the composite filament. Preferably, the filaments are heated at constant length after drawing, the duration and temperature of heating being sufficient to reduce the skein shrinkage," as hereinafter defined, to 5 percent or less. The temperature and time required to so stabilize the filament structure will vary depending on the filament denier, the heating arrangement employed, etc. However, temperatures in the range of 120--200 C. are usually satisfactory, the duration of heating being adjusted to give the desired shrinkage. Excessive heating must of course be avoided since this will result in loss of filament crimpability.

When the filaments of this invention are subjected to boiling water, or other treatment causing them to shrink, the filaments crimp in a helical configuration. Generally, the poly(ethylene terephthalate) component is predominantly on the inside of the helix in the crimped filaments.

The poly(ethylene terephthalate) and poly(1,4-cyclohexylene dimethylene terephthalate) employed in this invention are prepared by conventional methods which are well known in the art. Suitable procedures for preparing poly(ethylene terephthalate) are taught by Whinfield and Dickson in U.S. Pat. No. 2,465,319 and by Griffing and Remington in U.S. Pat. No. 3,018,272. The poly(1,4-cyclohexylene dimethylene terephthalate) may be in the cis or trans isomeric configuration or a mixture of the two. Poly(cyclohexylene dimethylene terephthalate) may be prepared as described in U.S. Pat. No. 2,901,466.

Either or both of the polymers used in preparing the bicomponent filaments may contain small amounts of additives such as delusterants, antioxidants, antistatic agents, surface-modifying agents, etc. Similarly, small amounts of other polymers may be present as melt blends or copolymers.

In order to equalize the melt viscosities of the two polymers at extrusion for ease of spinning, the relative viscosity of the poly(ethylene terephthalate) will usually be substantially higher than that of the poly(],4-cyclohexylene dimethylene terephthalate). However, if desired, a viscosity builder may be added to low-viscosity polymer or specially designed spinnerets as are known in the art, e.g. a spinneret with slanted orifices for the lower melt viscosity polymer, may be employed to overcome any processing difficulties resulting from differen'ces in melt viscosities.

Relative viscosity as referred to herein is a ratio of the viscosity of a 10 percent solution of the polymer in a mixture of 10 parts of phenol and 7 parts by wt. of 2,4,6- trichlorophenol to the viscosity of the solvent itself, both measured at 25 C. and expressed in the same units.

Skein shrinkage (abbreviated SS crimp index (Cl and crimp development (CD" are determined by the following procedure:

I. Prepare a sample of yarn or tow for testing as follows:

If a tow is to be tested, out a'length of about 30-50 centimeters and tie small loops at either end. One loop is used to hang the sample and the other for attachment of a weight. If a yarn is to be tested, prepare a skein of any convenient length and of about 1,500 denier. Obviously, the collapsed skein will be about 3,000 denier when loaded as a loop, and will be regarded as having about 3,000 denier for purposes of these determinations.

2. Apply a weight of 100 mg./den. and measure the length of the sample. In the case of atow sample, measure the length between the loops. Record this length as LE 3. Replace the 100 mg./den. weight with a weight of 1.5 mg./den. and again measure the length, LC

4. Remove the weight and-hang the sample in a container of gently boiling water so that the filaments are completely immersed for 5 minutes. The container should be deep enough so that the filaments do not touch the bottom. Remove the sample from the boiling water and allow the skein to hang without load for 1 hour or more to dry.

5. Pull the sample gently from both ends four times to straighten the filaments. Apply the same 1.5 mg./den. load as used in 3 above. Measure the sample length and and record as 6. Replace the 1.5 mg./den. load with the mg./den. load used in 2 above. Measure the sample length and record as LE Calculate the skein shrinkage, crimp index and crimp development by the following equations:

SS: (LEBBO LEABO) 100 Aao- 'iuao) 100 CD: LEABO surface and a 2-inch diameter glass is placed on the fabric.

The weight of the glass is sufficient to provide a load of 3 sm For greater a s, swsish s stasasss on top These data show that the filaments of this invention may be annealed at relatively high-temperatures to reduce fiber shrinkage while maintaining a good level of crimpability.

EXAMPLE 2 Three tows designated A, B, and C are prepared as in example 1 except that the tows are drawn at a ratio of 4.0 instead of 4.17 and the total denier of yarn C is reduced to give a drawn tow of 2.0 denier/filament as compared to 3.8 denier/filament for tows A and B. Table 11 below shows the ratio by wt. of the components in the filaments, the skein shrinkage, the crimp development at zero, 0.5 and 1.0 mg./den. load and the crimp index, C1. The crimp frequency, CF, i.e. the number of crimps per inch (cm.) of straightened yarn, after boiling and drying, is also shown.

TABLE II Anneal CF Polymer ratio temp. Yarn POHT/PET 0.) SS CD0 CD0, CD CI In. Cm.

A /70 160 1. 4 14. 4 14. 0 6. 9 0. 7 8 3. 1 B 50/50 160 1. 3 10. 4 8. 0 4. 9 0. 6 7 2. 8 C 50/50 120 3. 5 20. 6 11. 0 6. 8 0. 3 14 5. 5

the glass to give the desired loading. With a 40 g./cm. total weight, the method gives the BS1 bulk value; while at a 239 is determined separately on a representative sample and the bulk calculated from the following equation:

Fabric thickness, in. 749.12

Bulk (am/gram: Fabric wt., oz. sq. yd.

EXAMPLE l P0ly(1,4-cyclohexylene dimethylene terephthalate) prepared from 1,4-cyclohexane dimethanol containing about 70 percent of the trans isomer and having a relative viscosity -of 22 and poly(ethylene terephthalate) having a relative viscosity of 53 are melted and supplied to a spinneret assembly of the type described by Evans and Pierce in British Specification Pat. No. 1,075,689. The spinneret assembly is maintained at 312 C. The two polymers are extruded separately from pairs of closely spaced orifices so that the two polymers coalesce at the spinneret face to form side-by-side bicomponent filaments. in this manner 34 round bicornponent filaments are formed. Various ratios of the two polymers are extruded as shown in table 1 below. The filaments are quenched in a conventional manner, converged into 500 denier yarn and the yarn wound into packages at 300 yds./rnin. (274 meters/min.). Twenty-five ends of yarn are combined to form a tow which is then drawn while passing through a water bath at 90 C. for a distance of about 48 inches (122 cm.) the draw ratio being 4.17 and the draw roll surface speed 100 ft./min.

(30.5 meters/min). The yarn is then annealed at constant length by passage over heated rolls for 26 seconds. The temperature of the rolls is given in the table below. Skein shrinkage (SS) and crimp development (CD) values are determined on the tow and are shown in table I below. In the following tables poly( l ,4-cyclohexylene dimethylene terephthalate) is abbreviated PCHT," and poly(ethylene terephthalate) is abbreviated PET.

Tows A and B are cut to 3.5 inch (9 cm.) staple and a 2/21 worsted count yarn, 9.0 z/4.8 S turns per inch, is prepared on a worsted system from a 35/35/30 weight percentage blend of yarn A/yarn B/64-70 wool. The yarn is knit to a series of midbulky fabrics on a S-cut hand-knitting machine and piece dyed in the laboratory. The aesthetics of these piece-dryed fabrics are very desirable with good bulk and loft, and the handle is definitely worsted-like. As shown in table Ill below, the measured bulks (Fabrics 1,2 and 3 were significantly higher than that of /30 Dacronpolyester and wool fabric of similar weight and construction (fabric 4 What is claimed is: l. A crimpable composite textile filament having two iongitudinally extending components, one of said components consisting essentially of poly(l,4-cyclohexylene dimethylene terephthalate) and the other components consisting essentially of poly(ethylene terephthalate), said poly( 1,4-cyclohexylene dimethylene terephthalate), component being 15 percent to 70 percent by weight of said filament, the filament being characterized by having a Skein shrinkage (SS) no greater than 5 percent and a crimp development of at least 10 percent under no load (CD after boil off in boiling water for 5 minutes.

2. The filament of claim 1 having 30 to 60 percent by weight of said poly( l ,4-cyclohexylene dimethylene terephthalate) component.

3. The filament of claim 2 said filament being crimped in a helical configuration and having said poly(ethylene terephthalate) component predominantly on the inside of the helix.

4. A yarn comprising a plurality of composite staple fibers of the filament of claim 3. 

2. The filament of claim 1 having 30 to 60 percent by weight of said poly(1,4-cyclohexylene dimethylene terephthalate) component.
 3. The filament of claim 2 said filament being crimped in a helical configuration and having said poly(ethylene terephthalate) component predominantly on the inside of the helix.
 4. A yarn comprising a plurality of composite staple fibers of the filament of claim
 3. 